1. Field of the Invention
The present invention relates generally to a technique for fabricating integrated circuits and, more particularly, to a technique for fabricating content addressable memory devices.
2. Background of the Related Art
This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Microprocessor-controlled circuits are used in a wide variety of applications. Such applications include personal computers, control systems, telephone networks, and a host of other consumer products. A personal computer or control system includes various components, such as microprocessors, that handle different functions for the system. By combining these components, various consumer products and systems may be designed to meet specific needs. Microprocessors are essentially generic devices that perform specific functions under the control of software programs. These software programs are generally stored in one or more memory devices that are coupled to the microprocessor and/or other peripherals.
The memory devices include many different types of circuits that are typically formed using conductive, semiconductive and insulative materials. These circuits work together to allow the memory device to carry out and control various functions within an electronic device. One type of high-density memory device is a random access memory (RAM) device. Random access memory devices are complex integrated circuits which are fabricated using a variety of designs and fabrication techniques. Despite their complexity, manufacturers typically attempt to design memory devices that are inexpensive to manufacture, yet maintain high performance and reliability.
Random access memory devices, such as dynamic random access memory (DRAM) devices and static random access memory (SRAM) devices generally include a number of memory cells arranged in an array of rows and columns. The rows and columns provide signal paths to and from each memory cell in the array. Regardless of whether the device is a DRAM or SRAM, each memory cell generally includes one or more storage devices, such as capacitors, and one or more access devices, such as transistors. The access devices are generally coupled to the rows and columns of the array to provide access to the storage device. As can be appreciated, the rows and columns may also be referred to as wordlines and bitlines.
Another type of storage device that may be implemented in a system is a content addressable memory (CAM) memory device. A CAM memory device is a type of storage device which includes comparison logic in each memory cell, along the access and storage elements. CAM devices are designed to enhance data retrieval speed from a particular location in the memory array. Instead of using an address to read the data, as in a typical RAM device, the data is provided to locate the address in a look-up table for instance. The CAM device that is coupled to the storage portion of the memory cell is implemented to determine whether data is found within the particular cell of the memory array. When a match is found, the CAM device outputs the address location in the array. By sending a data value to each memory cell of the memory array and comparing it with the data stored therein, accelerated data searches may be performed in the memory array.
As can be appreciated, because DRAM-based CAM devices include a device to facilitate the data comparison, along with an access device and storage device, structural limitations resulting from high density fabrication techniques may provide designers with a greater challenge than with standard RAM devices. Reducing cell size without compromising device functionality provides DRAM-based CAM designers with a number of challenges.